Swammerdami
Squadron Leader
O God, let me try again.
O God? Is there's something wrong with the answers you've gotten?
The chance of reaching into the bucket and picking out a red ball are:
(20,000,000 / 52) = 384,615
Meaning that the probability of drawing out a red ball is 1 in 384,615 chances.
Just to be pedantic, a "chance" is a number in the interval [0, 1]. "1 in 384,615" is a chance. "384,615" is not.
I'm not particularly a fan of pedantry, but let's do our utmost here to strive for clarity.
What does "confident" mean to you? This drawing will fail 36.79% of the time. This, like everything else you ask, has been explained in the thread already.Meaning that I would have to reach into the bucket 384,615 times in order to be confident of drawing out a red ball.
OK ... if we agree on the above, then the chances of drawing out a red ball in a scoop of 20K balls is:
(384,615 / 20,000) = 19.23
Wrong. Let's see if we can agree on WHY it's wrong.
First, humor us, and use probabilities that are between 0 and 1. IOW, write (52 * 20000) / 20000000 = 1/19.23. (Your introduction of "384,615 " is just a distraction.) BTW, 1/19.23 is an approximation to the exact answer 5.2000000%. Do you see that?
But 0.052 is NOT the probability you will draw exactly one red, nor is it the probability you will draw at least one red. It is the number of reds you will draw on average.
The probabilities you will draw exactly 0, 1, 2, 3, 4 or 5 reds are
p0 = .9493041051
p1 = .0494133528
p2 = .0012612419 ~ .05^2 / 2!
p3 = .0000210397 ~ .05^3 / 3!
p4 = .0000002580 ~ .05^4 / 4!
p5 = .0000000025 ~ .05^5 / 5!
(I've shown the probabilities along with an approximation, mentioned upthread, that may be useful for quick estimates.)
p1 is 0.049..., not 0.052. To get 0.052 you'll need the sum p1 + 2*p2 + 3*p3 + 4*p4 + ...
Does any of this help?
If we can just settle that for the moment then we can look at shades of red later. OK?
cheers ... Greg
When we look at shades of red, please clarify the ambiguity identified above in #17 ( "(a) or (b)" ).